Many electromagnetic launch systems including electrothermal and electrothermal-chemical guns are known. The majority of them make use of capacitive-based pulsed forming networks (PFN) for launcher energizing. However, capacitive storage possesses low energy density, and hence system volume is unacceptably large for practical applications. Inductive storage systems possess much higher energy density, but their implementation is hampered by lack of compact, repetitive, inexpensive and robust opening switches.
An implementation of an opening switch in an inductive power supply known in the art is shown in FIG. 1 as described in Pokryvailo, A., Kanter, M. and Shaked, N., “Two-Stage Opening Switch for Inductive Energy Storage Systems”, IEEE Trans. on Magnetics, Vol. 34, No. 3, pp. 655-663, May 1998. The primary power source, Vb, is a battery bank. The opening switch comprises a vacuum circuit breaker, employed as a closing switch and as the first stage of the opening switch, and a fuse serving as the second stage. An SCR (Silicon-Controlled Rectifier) in series with the fuse blocks the battery voltage during the coil charge, while diode D blocks the load; the latter can be an electromagnetic launcher.
Upon the vacuum breaker closing, the coil L is charged. The switching sequence begins with the breaker opening at time t0, as shown in FIG. 2. When the voltage across its contacts exceeds the comparator reference voltage, the comparator fires the SCR. Driven by the arc voltage, the charge current passes to the fuse in the interval t0-t1. The fuse current, if, flows during interval t1-t2 to enable a sufficient separation d of the contacts, and thus the recovery of the vacuum breaker dielectric strength during the current zero pause. Upon the fuse blowing, the opening sequence is accomplished by the current transfer to the load, when the voltage is inductively generated across the switch and the load.
However, in this implementation, fuses must be assembled in a cassette to enable repetitive operation, increasing the system volume and cost.